1. Field of the Invention
The present invention relates to a liquid discharging head and a method for producing the liquid discharging head.
2. Description of the Related Art
There has been known a liquid discharging head formed of a plurality of stacked plates, having liquid channels which are formed by making openings formed in the respective plates communicate with one another, and discharging, from nozzles, a liquid flowing through the liquid channels.
In recent years, as the specifications of a liquid discharging head have become diversified, its producing methods have also become diversified. For example, the use of metal diffusion bonding for bonding plates to form a channel unit has an advantage of realizing firm bonding strength and excellent durability. Further, the number of processes can be reduced since the plural plates can be bonded at a time. Moreover, production cost can be reduced since a plurality of (several thousand) channel units can be produced at a time by batch processing. Further, the plates bonded by metal diffusion bonding have an advantage that they do not easily peel off from one another even if the plates are exposed to high temperature.
However, in a case where metal diffusion bonding is used to form the channel unit, the plates cannot be torn off after bonded. Therefore, even if steps and gaps occur in liquid channels due to, for example, positional deviation or shift of openings formed in the plates, it is not possible to tear off the plates to correct the positional deviation or shift. In the steps and gaps occurring in the liquid channels, bubbles contained in the liquid easily stay, and these bubbles prevent the smooth flow of the liquid. Further, it is difficult to discharge these bubbles even by purging. Further, if steps and gaps occur in descenders each of which communicates a nozzle and a pressure chamber for applying jetting pressure to the liquid, a pressure wave attenuates, resulting in low driving efficiency of an actuator. Thus, the head formed by metal diffusion bonding has problems that bubbles easily stay in the steps and the gaps occurring in the liquid channels and the bubbles prevent stable discharge of the liquid. Another problem is that the pressure wave attenuates due to the steps and the gaps, resulting in low driving efficiency of the actuator.
Japanese Patent Application Laid-open No. H11-300951 discloses an ink-jet head producing method in which, before a top plate having grooves is bonded to a substrate having discharge energy generating elements disposed on part of nozzles, a mixture of resin and air is sprayed to a bonding surface side of the top plate, thereby making surfaces of the nozzles curved in a cross-sectional view.
However, since the ink-jet head producing method described in Japanese Patent Application Laid-open No. H11-300951 is to make the surfaces of the nozzles curved in the cross-sectional view before bonding the top plate and the substrate. Therefore, this method is not applicable to steps which occur after a plurality of plates are bonded by, for example, metal diffusion bonding or the like, as a result of shift or positional deviation of openings formed in the plates.